hi ralf: Thanks for your reply :) 2011/10/17 Ralf Baechle <ralf@xxxxxxxxxxxxxx>: > On Mon, Oct 17, 2011 at 07:36:11PM +0800, loody wrote: > >> Dear all: >> I have some questions about local_flush_tlb_one. >> 1. what will happen if I use local_flush_tlb_one to flush a page that >> doesn't exist in translation lookaside buffer entries. >> >> The index return by read_c0_index(), should be negative. >> but this function seems not handle the case that idx < 0. >> >> 2. as I know, translation lookaside buffer is a place to keep record >> the memory mapping, it doesn't like cache have place to store the >> data. >> a. If the entry is cacheable, what we only to do is flush the cache? >> b. if the entry is uncached, there is nothing to do? >> if above b is correct, what will happen if we have an entry that is >> uncached and dirty? > > If c0_index contains a value < 0 (or rather one with bit 31 set) then > there is nothing that needs to be flushed. but how about the case of c0_index >= 0, I found the code tried to write the index with entry_lo0 and entry_lo1 as 0. it seems clear the PFN part of the index. So it is the flush action? > > Note that MIPS D-cache (I-caches don't get written back so are not of > concern) are tagged with a physical address so cache handling is no > consideration for local_flush_tlb_one or any of the other TLB flush > functions. why tlb flush functions don't need to take care cache handling? if tlb flush don't need to care cache, what is tlb flush used for, since tlb is nothing but a place to do the address translation, right? -- Appreciate your help,
